Microstructured surfaces have been prepared by many different types of chemical and physical deposition processes. These processes are conveniently categorized as "wet chemical" processes and "dry chemical" processes. An example of a wet chemical process involves exposure of aluminum, magnesium, or zinc metal film or alloy thereof to saturated steam or an aqueous oxidizing solution to form an oxyhydroxide boehmite microstructured surface (see U.S. Pat. Nos. 4,123,267; 4,190,321; 4,252,843; 4,396,643). An example of a dry chemical process involves production of thread-like, non-uniform, mosaic structures of randomly oriented alpha- and beta-copper phthalocyanine crystallites by annealing, in air, films of copper phthalocyanine that had been vapor deposited in vacuum on glass and potassium chloride substrates, or by vapor deposition of copper phthalocyanine on a heated substrate (see "Thermal Behavior of Thin Copper - Phthalocyanin Films", O. Hirabaru, T. Nakadhima, H. Shirai, Vacuum (Japan) 22(7) (1979) 273).
In most applications of the aforementioned wet chemical and dry chemical) processes, the microstructured surfaces are generally made of metallic or inorganic materials only. In addition, the microstructured surface comprises a polycrystalline or amorphous material, not single crystalline material.
Microstructured surfaces currently in use and the processes used to make them have one or more shortcomings. Some have wide variation in the size distribution or aspect ratio of the microstructure. This variation renders the properties of the microstructured surface difficult to specify, making the surface a poor candidate for optical uses such as absorption or reflectivity. Some microstructures are peculiar to specific substrates, many of which are subject to corrosion Some microstructured surfaces are opaque to electromagnetic radiation. This limitation precludes their use with transparent media. Most of the aforementioned dry processes rely on a dynamic method of forming microstructures during the step of film deposition, which necessarily involves either multiple deposition parameters that can be difficult to control in practice or non-equilibrium growth mechanisms that are unpredictable. In addition, many of the dry or wet chemical processes are suitable for imparting microstructures to only relatively small surface areas during a given time period due to limitations of available equipment.